Free piston engine



w. KlLcl-IENM-ANN 2,425,375

FREE PIS'ION ENGINE File@ oct. 2, 1945 f6 f77/85 f3 43 :a 2 4.3/6 /7 ,5.

Aug. 12, 1947.v

INVENTOR WALTER /r/c//ENMANN ATTORNEYS Patented Aug. 12, 1947 f FREE Prs'roN ENGINE Walter Kilchenmann, Winterthur, Switzerland, assigner to Sulzer Frres, Societe Anonyme,

Winterthur, Switzerland Application october z, 1945, serial No. 619,883 Inswmeriana Aprilia, 194s 9 Claims. (Cl. 23o-56) The invention `relates to a free piston engine and consists in that at least one compressor piston is detachably connected to an internal comlbustion piston in such a way that the interna-l combustion pistonl can be built into the engine and removed from it through the compressor piston.

By the invention, the advantage is obtained that the overhaul of the internal combustion piston can be efl'ected without dismantling the corresponding compressor piston. Since the internal combustion piston must be cv'erhauled oftener than the compressor piston, a considerable saving ot time'and money is attained by the invention.

Several embodiments of the subject matter of the invention `are illustrateddiagrammatically in Jecting member 9, whose flange I is fixedl to the cover I I of the compressor cylindert, serves as a buii'er piston. Buffer piston v9 works in the builercylinder II' formed in the interior of the internal combustion piston 3.

The intake system to the compressor cylinders 5, 6 comprises the intake branches I4, the annular intake` manifold spaces I and the intake valves IB. On the inward stroke of compressor pistons 1; 8 valves I 6 open to admit air from intake manifold spaces I5 tothe compressor cylinder through passages I1. 0n the outward stroke of pistons 1, -8 valves IB close, but valves It'open and compressed air is delivered back through passages I1 to the delivery space I9 which forms the casing of the whole free-piston engine I.

When-the outlet ports are uncovered by the piston 3 and the inlet ports '2i are uncovered somewhat later by the piston 4, the combustion gases flow through the ports 20 into the exhaust branch 22, while the air from the space I9 enters through the ports .ZI into the internal combustion cylinder 2, scavenges out the combustion gases and illls the cylinder with fresh air. The air pressure and the quantity o1' excess air are adjusted in accordance with the purpose for which the free piston engine is used, i. e. whether it works as a power` gas producer or in some other manner. A machine using power gas, for instance a gas turbine for giving useful energy from the plant, may be connected to the exhaust branch 22. During the inward stroke of the pistons 3 'and 4, they ports 2I and also the ports 20 are closed, and the air in the internal combustion cylinder 2 is so highly compressed that the fuel injected through the fuel valve 23 is ignited and burnt, after which a new expansion stroke takes place. The fuel is supplied by a fuel pump (not shown in the drawing), which is driven for instance by the rack coupling gear 42 between the pistons 'I and 'l The compressor cylinders 5 and 6 are connectedltoeach other and to the rack spaces by means of the openings 43. For the sake of simplicity, the cooling system of the internal combustion cylinder, lubrication and other details irrelevant to this Invention have been omitted from the drawing. f

' Pistons 3 and 4 are provided on their outer ends with flanges '24 which lie on theV outer ends of compressor pistons I and 8, respectively and are firmly fixed thereto by means of the screwsi25. In consequence of this construction of the compressor pistons and of the detachable connection by means of the iianges 24, the internal combustion pistons can, as shown for the piston 4 in the` drawing, be built into the engine or removed from it through their corresponding compressor pistons. It is, however, not necessary for both internal combustion pistons to be xed in this manner. It would be pOssible to fix only the piston 4 as described, and to fix the piston 3 to the inner y side of the compressor pistoni, so that the piston 3, after this connection has been detached, would be removed from the engine through the cylinder 2 Aand the compressor piston 8, at the same side of the engine as the piston 4. In this way, it would not be necessary to provide spaces for dismantling at both sides of theengine I. Particularly in the case ofk vertically arranged internal combustion cylinders, the removing of the two internal combustion pistonsV fromabove would Y help to reduce the height of the engine.

internal combustion pistons is the smallest possible. jand also the compressor pistons 'I and 8 and the The large compressor covers il and I2,

coupling rods connected to the latter. remain untouched.

` In order that the central .position of the compressor pistons 1 and 8 may remain unaiected when removing and inserting the internal com- 1bustion pistons 3 and l, centering additions 28, 29 with tapered surfaces are provided Von the covers il and i2 and on the ends oi the internal combustion cylinder 2. The pistons 1 and 8 are,

las shown in the compressor cylinder pressed by means ci a screw thread 34 on the internal combustion piston 4, which is screwed into the compressor piston S.

In Fig. an annular screw 35 with internal and external threads and end flange 36 is provided a detachable connection between the internal combustion piston land the compressor piston 8. By means of this, it is possible to use an ordinary piston ring compressor or other tool adding to the overallY 'diameter of the part to be inserted for the piston rings even when the compresser piston 8 is centered against the cylinder cover l2 when removing the internal combustion piston d.

1 Figs, 4 and 5 show a detachable connection formed in the manner of a bayonet joint. The internal combustion piston 4 is provided with lips 31 which are brought in front of the openings `38 in' the compressor piston by rotating'theinternal combustion piston with reference to the compressor piston. The openings 38 are covered completely by means of the flange 39 when assembling. In order to obtain a rm connection, the lips 3T and the lips 40 are bevelled between the openings 38 on their contact surfaces, so

that when turned .ml one direction, for instance clockwise, a slight lpull is eiected. For loosening, the turning must then be done in the opposite direction. The securing pin Il prevents the pistons 4 and 8 from becoming loose after being assembled together.

i I claim: l. A free piston engine havingV a compressor cylinder closed by a cover, an internalcombustion cylinder connected to thevcompressor cylinder, a compressorpiston arranged in said compressor cylinder, an internal lcombustion piston working in said internal combustion cylinder, said internal combustion piston being detachably connected to said compressor piston, and said cover being tted with a closable opening so that the internal combustion piston can be built into the engine and removed from it through the compressor piston and through the cover without removing the compressor piston and thevcover.

t vided at thelend with a nange which is fixed to 2. A free piston engine as claimed in claim 1, the internal combustion piston of which is prothe outer surface of the compressor piston. 3. A freev piston engine having a compressor cylinder closed by a cover, an internal combustion cylinder connected to the compressor cylinder, a compressor piston arranged in said compressor cylinder, an internal combustion piston working in said internal combustion cylinder, and a buffer 1 piston, said internal combustion piston being l formed as abuier cylinder in order to guide the o bun'er piston and being detachably connected to the compressor piston,` said cover being tted with an opening closable by means of the buffer l piston so that, `vafter dismantling the buier piston, the internal combustion piston can bev dismantled throughrthe opening thus produced.`

4. Freepiston engine as claimed in claiml, the compressor .piston of which and the cover of the compressor cylinder being provided with recesses "or bores, each or which can be" brought lopposite to each otherv so that the compressor piston can i positionfor bulldinginvor`removing the internalv Y which vthe internal combustion'cylinder structure be held nrmly lby means of bolts in one or other end position, in order to be able tohold the com'` pressor piston rmly in'the innerv or outer end combustion piston. l

5. Free piston engine as claimed in claim 1in which the cover carries means for centering the compressor piston. y

6. Free piston yengine as claimed in claim 1 in carries means for centering the compressor piston.

7. Free piston engine as claimed inclaim 1 in I which the internal combustion piston is attached relation to one another whereby thetwo pistons Y to the compressor'piston by means of a bayonet Joint.. v

8. Free piston engine as claimed in claim 1 in which the internal combustion piston is attached to thel compressor piston by means of a bayonet joint, the portions of said joint carried-by each of said pistons having contact. surfaces bevelled in y are forced into tight engagement when subjected toa relative rotation.

9. Free piston engine asl claimed in claim 1 in which the internal combustion pistonis attached to the compressor Ipiston by means of an inter- The following references are of record in the nallyand externally-threaded sleeve.

' WALTER HLCHENMANN.

REFERENCES CITED ille of'this patent:

' UNITED STATES PATENTS France Jan. 16, 1933 

